Measurement properties of the benign prostatic hyperplasia impact index in tadalafil studies

BACKGROUND: To assess the measurement properties of the Benign Prostatic Hyperplasia Impact Index (BII) for use in men with Lower Urinary Tract Symptoms (LUTS) secondary to Benign Prostatic Hyperplasia (BPH) treated with tadalafil. METHODS: Data from a dose-titration (Study 1) and a dose-finding placebo-controlled (Study 2) tadalafil studies of men 45 years of age or older with moderate to severe LUTS (N = 281; N = 1053) were included in this post-hoc analysis. Measures included the BII, International Prostate Symptom Score (IPSS), IPSS Quality of Life Index (IPSS-QoL), LUTS Global Assessment Question, uroflowmetry measure peak flow rate (Q(max)) and postvoid residual volume (PVR). Spearman rank and Pearson correlation coefficients were computed between the BII score and the other measures at each visit. Wilcoxin two-sample tests, t-tests and general linear modeling compared BII scores of subjects with global ratings of improvement versus no improvement, and subjects taking tadalafil versus placebo. Effect size, standardized response mean and Guyatt's responsiveness statistic were calculated for BII and IPSS change scores. RESULTS: There were high correlations between BII and IPSS & IPSS-QoL and low correlations between BII and Q(max )& PVR at each visit. There were significant differences in BII at the End-of-Study Visit between subjects reporting improvement versus subjects reporting no improvement (Studies 1 and 2, P < .0001) and subjects taking tadalafil versus subjects taking placebo (Study 1, P = .0045; Study 2, P = .0064). The BII and IPSS were both responsive to change. CONCLUSIONS: Results show that the BII is reliable, shows responsiveness to change in patients with BPH-LUTS, and demonstrates construct validity.